1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly to a light guide device, and a liquid crystal display module and a liquid crystal display device having the light guide device, which can minimize the flowing of a light guide plate received in a mold frame by improving the structure of the light guide plate of the liquid crystal display device.
2. Description of the Related Art
Recently, an information processing device has been developed to have a various shape, a various function, and a rapid information processing speed. The information processed in the information processing device has an electrical signal. In order to confirm the information processed in the information processing device with the naked eye, a display device that is needed.
Recently, a liquid crystal display device which is lighter, and smaller than a CRT type display device has been developed. The liquid crystal display device now displays a full color spectrum in a high resolution. As a result, the liquid crystal display device is widely used as a computer monitor, a television receiver, and another display device.
The liquid crystal display device applies a voltage to a liquid crystal layer to change the molecular arrangement of the liquid crystal layer. The liquid crystal display device changes of optical properties in the liquid crystal and uses the modulation of a light by using a liquid crystal cell.
There are two kinds of liquid crystal display devices: TN (Twisted Nematic) method; and an STN (Super-Twisted Nematic) method. Also they can be grouped to an active matrix display method that uses a switching device and a TN liquid crystal, and a passive matrix display method which uses a STN liquid crystal according to the driving type.
The active matrix display method is used in a TFT-LCD and drives an LCD by using a TFT as a switch. The passive matrix display method does not use any transistor and does not need a complex circuit.
Further, liquid crystal display devices are grouped to a transmissive liquid crystal display device that uses a backlight and a reflecting liquid crystal display device that uses an exterior light source, according to a method for using a light source
The transmissive liquid crystal display device using the back light as a light source is relatively heavy and voluminous due to the back light, but is widely used since it does not use an exterior light source and displays independently.
FIG. 1 is an exploded perspective view schematically showing a conventional liquid crystal display device. FIG. 2 is a partial exploded perspective view of the liquid crystal display device shown in FIG. 1.
Referring to FIG. 1, the liquid crystal display device 900 has a liquid crystal display module 700 to which an image signals is applied to display the screen, and a front surface case 810 and a rear surface case 820 for receiving the liquid crystal display module 700.
The liquid crystal display module 700 has a display unit 710 which includes a liquid crystal display panel for displaying the screen.
The display unit 710 has a liquid crystal display panel 710, an integrated printed circuit board 714, a data side tape carrier package 716, and a gate side flexible circuit board 718 manufactured by the COF method.
The liquid crystal display panel 712 has a thin film transistor substrate 712a, a color filter substrate 712b, and a liquid crystal layer interposed therebetween (not shown).
The thin film transistor substrate 712a is a transparent glass substrate on which thin film transistors are formed in a matrix shape. Data lines are connected to source terminals of the thin film transistors, and gate lines are connected to gate terminals of the thin film transistors. Pixel electrodes of indium tin oxide (ITO), which is a transparent conductive material, are formed on drain terminals.
If electrical signals are inputted to the data lines and the gate lines, the electrical signals are inputted to the source terminals and the gate terminals of thin film transistors and the thin film transistors are turned on or off so that electrical signals for forming pixels are outputted to the drain terminals.
The color filter substrate 712b is attached to the thin film transistor substrate 712a. RGB pixels that pass light through to realize color display is formed on the color filter substrate 712b by a thin film process. A common electrode comprised of ITO is coated on the front surface of the color filter board 712b. 
If power sources are applied to the gate terminals and the source terminals of the transistors and the thin film transistors are turned on, an electric field is formed between the pixel electrode on the thin film transistor substrate and the common electrode on the color filter substrate. The arrangement angles of the liquid crystals injected between the thin film transistor board 712a and the color filter board 714b changes by the electric field, and the light passage changes due to the arrangement angle changes to obtain a desired pixel status.
A driving signal and a timing signal is applied to the gate line and the data line of the thin film transistor to control the arrangement of the liquid crystal of the liquid crystal display panel 712 and the timing when the liquid crystal is arranged. The data side tape carrier package 716 which is a kind of flexible circuit board determining the timing when the data driving signal is applied is attached to the source side of the liquid crystal display panel 712, and the gate side flexible circuit board 718 manufactured by the COF method for determining the time at which the gate driving signal is applied is attached to the gate side of the liquid crystal display panel 712.
The integrated printed circuit board 714 for receiving image signals from outside of the liquid crystal display panel 712 and applying driving signal to the gate line and the data line is connected to the data tape carrier package 714 of the data line side of the liquid crystal display panel 712. The integrated printed circuit board 714 has a source portion to which the image signals generated in an exterior information processing device (not shown) such as a computer are applied to provided the data driving signals to the liquid crystal display panel 712 and a gate portion for providing the gate driving signals to the gate line of the liquid crystal display panel 712. Namely, the integrated printed circuit board 714 generates the gate driving signals for driving the liquid crystal display device, the data signals, and a plurality of timing signals for applying the signals. The gate signals are applied to the gate line of the liquid crystal display panel 712 through the gate side flexible circuit board 718, and the data signals are applied to the data line of the liquid crystal display panel 212 through the data tape carrier package 716.
A back light assembly 720 for providing a uniform light to the display unit 710 is provided under the display unit 710. The back light assembly 720 comprises a lamp 722 which is provided on one side of the liquid crystal display module 700 to generate the light. The lamp 721 is protected by a lamp cover 722. A light guide plate 724 has a size corresponding to the liquid crystal display panel 712 of the display unit 710, and is located under the liquid crystal display panel 712. The lamp side of the light guide plate 724 is thicker than the other side, and guides the light generated in the lamp 722 towards the display unit 710 to change the passage of the light.
A plurality of optical sheets 726 for making the luminance of the light irradiated from the light guide plate 724 and passed towards the liquid crystal display panel 712 uniform are provided above the light guide plate 724. A reflection plate 728 for reflecting the light leaking from the light guide plate 724 to increase the light efficiency is provided under the light guide plate 724.
The display unit 710 and the back light assembly 720 is fixed and supported by a mold frame 730 that is a receiving receptacle. The mold frame 730 has a box-shape, and the upper surface of the mold frame 730 is open. Namely, the mold frame 730 has four side walls and a bottom, and openings for bending the integrated printed circuit board 714 along the outer side surface of the mold frame 730 and positioning the integrated printed circuit board 714 are formed on the lower surface of the bottom.
A chassis 740 for bending the integrated printed circuit board 714 of the display unit 710 and the gate tape carrier package 718 outside of the mold frame 730 and fixing the integrated printed circuit board 714 of the display unit 710 and the gate tape carrier package 718 to the bottom surface of the mold frame 730 to prevent the deviation of the display unit is provided. The chassis 740 has a box-shape. The upper surface of the chassis 740 is opened to expose the liquid crystal display panel 710, and the side walls are bent inwardly to cover the upper surface peripheral portion of the liquid crystal display panel 710.
On the other hand, referring to FIG. 2, first and second catching bosses 731 and 732 integrally formed with the mold frame 730 are formed on the corner portion of the side wall of the side on which the lamp 721 is installed in the receiving space of the mold frame 730. The lamp side corner of the light guide plate 724 received in the mold frame 730 is cut off to form first and second catching jaw 724a and 724b. 
FIG. 3 shows the state in which the light guide plate shown in FIG. 2 is received in the mold frame. FIG. 4 is a partially enlarged view for showing the fixing structure of the light guide plate shown in FIG. 3 and the mold frame. FIG. 5 is a top view for showing the size of the light guide plate shown in FIG. 3.
Referring to FIG. 3, if the light guide plate 724 is received in the mold frame 730, the first and second catching jaws 724a and 724b are engaged with the first and second catching bosses 731 and 732. Therefore, even when exterior impacts are applied to the liquid crystal display device 900, the light guide plate 724 is does not move to the lamp side due to the first and second catching bosses 731 and 732.
However, recently, the side wall of the mold frame 730 is getting thinner to minimize the size of the liquid crystal display device 900. Further, as shown in FIG. 5, the width of the light guide plate 724 of the end portion of the side of the lamp 721 is identical to the width of the end portion of the opposite end portion. Therefore, it is not easy to sufficiently guarantee the thickness of the first and second catching bosses 731 and 732 which are integrally formed with the mold frame 730. Therefore, as shown in FIG. 4, the catching amount of the first and second catching jaws 724a and 724b of the light guide plate 724 and the first and second catching bosses 731 and 732 of the mold frame 730 can not be sufficiently guaranteed, making it difficult to prevent the light guide plate 724 from moving to the side of the lamp 721.
On the other hand, if the width of the light guide plate 724 is increased by the gap between the light guide plate 724 and the mold frame 730 to guarantee the catching amount, the catching amount of the first and second catching jaws 724a and 724b and the first and second catching bosses 731 and 732 can be obtained. However, without the gap between the light guide plate 724 and the mold frame 730, the thermal expansion space of the light guide plate 724 according to the temperature change and the humidity cannot be guaranteed, deteriorating the folding phenomenon. Especially, in the wedge type light guide plate 724 shown in FIG. 1, since the thermal expansion rate is large at a portion the light guide plate 724 is thin, the gap between the light guide plate 724 and the mold frame 730 needs to be sufficient.
On the other hand, even if it is not shown, the flowing of the light guide plate 724 can be prevented by protruding a portion of both side surfaces of the light guide plate 724, forming a boss, and forming a recess at a position which corresponds to the boss on both side wall of the mold frame 730. However, in the case, it is not easy to guarantee the catching amount between the boss and the recess and the light inputted from the lamp is concentrated at a corner portion bent by the boss and the recess.